It is very old to have stands whose height can be adjusted. A typical stand of this type is an ironing board stand. There are, however, numerous other stands for adjustably supporting a relatively light load at any of selected heights.
While such prior art devices are in many cases well suited to the purposes for which they were designed, they would be completely useless for supporting very heavy loads such as are often encountered in a factory or machine shop. Often, the load which is to be supported is a pallet which, in turn, is loaded with heavy materials such as machine parts. To provide a stand which will support such heavy loads requires the use of very strong structural elements such as beams. When this is done, the movable elements of the stand become so heavy that it becomes extremely difficult for the user to adjust the height of the stand. When the stand is folded, it becomes extremely difficult for the user to lift the stand to its extended position.